Anti-fungal agents and methods of identifying and using the same

ABSTRACT

PCT No. PCT/US96/09530 Sec. 371 Date Mar. 23, 1998 Sec. 102(e) Date Mar. 23, 1998 PCT Filed Jun. 7, 1996 PCT Pub. No. WO96/40886 PCT Pub. Date Dec. 19, 1996Substantially pure C. albicans topoisomerase I protein is disclosed. Nucleic acid molecules that encode C. albicans topoisomerase I protein, recombinant expression vectors that comprise a nucleic acid sequence that encodes C. albicans topoisomerase I protein, and host cells that comprise recombinant expression vectors that comprise nucleic acid sequences that encode C. albicans topoisomerase I protein are disclosed. Fragments of nucleic acid molecules with sequences encoding C. albicans topoisomerase I protein and oligonucleotide molecules that comprise a nucleotide sequence complementary to fragment of a nucleotide sequence that encodes C. albicans topoisomerase I protein are disclosed. Antibodies which bind to an epitope on C. albicans topoisomerase I protein are disclosed. Methods of identifying inhibitors of C. albicans topoisomerase I protein are disclosed. Camptothecin analogs useful as inhibitors of C. albicans topoisomerase I protein are disclosed and methods of using camptothecin analogs as inhibitors of C. albicans topoisomerase I protein are disclosed.

CROSS REFERENCE TO RELATED APPLICATION

This application is a 371 of PCT application PCT/US96/09530 filed Jun. 7, 1996, and a continuation of Ser. No. 08/485,621 filed Jun. 7, 1995, issued as U.S. Pat. No. 5,691,187 and a provisional application Ser. No. 60/000,399 filed Jun. 21, 1995.

FIELD OF THE INVENTION

The invention relates to the identification and cloning of the topoisomerase I gene (TOP1) from Candida albicans and the use of the gene in complementation assays to identify inhibitors of the C. albicans TOP1 while having no effect on the homologous human TOP1. The invention relates to compounds that selectively inhibit C. albicans TOP1 and the use of such compounds to kill fungi and in the treatment of individuals with fungal infections.

BACKGROUND OF THE INVENTION

Candida albicans is the most important fungal pathogen infecting humans. This fungal pathogen causes vaginal yeast infections, as well as oral infections and tissue invasion in immunocompromised patients. Oral infections are highly prevalent in AIDS patients and in cancer patients undergoing bone marrow replacement therapy. Only three types of anti-fungal drugs are currently approved for use in humans. Unfortunately, these anti-fungal drugs have serious side effects and have limited efficacy.

Yeast Saccharomyces cerevisiae strains that express DNA topoisomerase I and are permeable to the anti-tumor alkaloid camptothecin compounds are killed by the compound (Nitiss, et al., Proc. Natl. Acad. Sci. USA, 1988, 85, 7501-7505). Yeast strains which are permeable to camptothecin but lack topoisomerase I can establish sensitivity to camptothecin by expression of human DNA topoisomerase I (Bjornsti, et al., Cancer Res., 1989, 49, 6318-6323). Thus, yeast cells lacking endogenous topoisomerase I are killed by camptothecin if they express human topoisomerase I. Camptothecin kills such yeast strains by stabilizing a covalent topoisomerase I-DNA conjugate which leaves a broken DNA strand. The broken single strand can be processed to a double-strand break during DNA replication. If this damage is not repaired by DNA recombination, it leads to cell death. Camptothecin, however, is not a candidate for human therapy for fungal-associated conditions due to its activity on human topoisomerase I.

There is a need for compounds which selectively inhibit C. albicans topoisomerase I activity but which do not inhibit human topoisomerase I activity. There is a need for kits and methods of identifying such compounds. There is a need for isolated C. albicans topoisomerase I protein, and for compositions and methods of producing and isolating C. albicans topoisomerase I protein. There is a need for methods of treating individuals that have fungal infections.

SUMMARY OF THE INVENTION

The present invention relates to substantially pure C. albicans topoisomerase I protein.

The present invention relates to substantially pure C. albicans topoisomerase I protein having the amino acid sequence of SEQ ID NO:2.

The present invention relates to nucleic acid molecules that encode C. albicans topoisomerase I protein.

The present invention relates to nucleic acid molecules encoding C. albicans topoisomerase I protein that consists of SEQ ID NO:1.

The present invention relates to recombinant expression vectors that comprise a nucleic acid sequence that encodes C. albicans topoisomerase I protein.

The present invention relates to host cells that comprise recombinant expression vectors that encode C. albicans topoisomerase I protein.

The present invention relates to fragments of nucleic acid molecules with sequences encoding C. albicans topoisomerase I protein that have at least 10 nucleotides.

The present invention relates to oligonucleotide molecules that comprise a nucleotide sequence complimentary to a nucleotide sequence of at least 10 nucleotides of SEQ ID NO:1.

The present invention relates to isolated antibodies which bind to an epitope on SEQ ID NO:2.

The present invention relates to host cells that have deficient or non-functional endogenous topoisomerase I proteins and comprise recombinant expression vectors that encode C. albicans topoisomerase I protein.

The present invention relates to methods of identifying inhibitors of C. albicans topoisomeerase I protein. The methods comprise contacting a first host cell which is deficient in a functional topoisomerase gene except for a functional gene that encodes C. albicans topoisomerase I protein with a test compound, contacting a second host cell which is deficient in a functional topoisomerase gene except for a functional gene that encodes non-C. albicans topoisomerase I protein with a test compound, and identifying a test compound whose presence results in the death of the first host cell but not the second host cell.

The present invention relates to compounds that are specific inhibitors of C. albicans topoisomerase I protein which selective inhibit C. albicans topoisomerase I protein. The compounds of the invention inhibit C. albicans topoisomerase I protein much greater than they inhibit human or other non-C. albicans topoisomerase I protein such that the compounds of the invention are lethal to C. albicans through the inhibition of activity of C. albicans topoisomerase I protein but that do not kill non-C. albicans species which come into contact with the compound.

The present invention relates to compounds that are Camptothecin analogs which selectively inhibit C. albicans topoisomerase I. Camptothecin analogs of the invention interact or otherwise interfere with the residues in the active site region of the C. albicans topoisomerase I, particularly the Methionine residue at Met736 which is present in C. albicans instead of the leucine located 2 residues amino-terminal to the active site tyrosine, Tyr738, found in human topoisomerase I.

The present invention relates to methods of treating individuals who have fungal infections comprising the step of administering to such individuals a therapeutically effective amount of a compound of the invention.

The present invention relates to methods of preventing fungal infections in individuals comprising the step of administering to such individuals a prophylactically effective amount of a compound of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides the cloned gene that encodes C. albicans topoisomerase I protein. The discovery of the C. albicans topoisomerase I gene and the protein that it encodes provides the means to design and discover specific inhibitors of C. albicans topoisomerase I protein.

As used herein the terms "specific inhibitor of C. albicans topoisomerase I protein" and "selective inhibitor of C. albicans topoisomerase I protein" are used interchangeably and are meant to refer to compounds that result in the death of C. albicans through the inhibition of activity of C. albicans topoisomerase I protein but that do not kill non-C. albicans species which come into contact with the compound. Compounds that selectively inhibit C. albicans topoisomerase I activity are those which inhibit C. albicans topoisomerase I activity but not the activity of non-C. albicans topoisomerase I proteins.

According to one aspect of the present invention, the gene that encodes C. albicans topoisomerase I protein may be used to produce recombinant microorganisms that are useful to screen compounds for specific inhibitors. A host organism deficient in endogenous topoisomerase I protein may be "complemented" with C. albicans topoisomerase I, i.e. furnished with a functional copy of the C. albicans topoisomerase I gene or cDNA. Expression of the nucleotide sequence that encodes C. albicans topoisomerase I protein results in production of functional protein which functions in place of the missing or non-functional endogenous topoisomerase I. Comparative studies can be performed to evaluate the effect test compounds have on the hosts that are complemented with C. albicans topoisomerase I compared to the effect the same test compounds have on the hosts with functional endogenous topoisomerase I or hosts that are complemented with non-C. albicans topoisomerase I. In some preferred embodiments, inhibitors are identified using complementation assays in which a first host cell that expresses C. albicans topoisomerase I protein to survive is contacted with a test compound and a second host. cell which expresses a non-C. albicans topoisomerase I protein to survive is contacted with the same test compound. If the first host cell dies in the presence of the test compound but the second host cell lives in the presence of the same test compound, the compound is indicated to be an inhibitor of C. albicans topoisomerase I protein.

Complemented host cells are deficient for functional endogenous topoisomerase I and rely on the activity of "foreign" topoisomerase I for survival. Host cells that are deficient for functional endogenous topoisomerase I and which can be complemented by "foreign" topoisomerase I for survival include yeasts, Saccharomyces species, Schizosaccharomyces species, Escherichia coli, and Salmonella typhimurium. In some preferred embodiments, complemented host cells are yeasts. In some preferred embodiments, complemented host cells are yeast: strain L1242, which is described in Thrash, et al., Proc. Natl. Acad. Sci. USA, 1985, 82, 4374-4378, which is disclosed in its entirety herein by reference, or other top1⁻ yeast strains.

Expression of human TOP1 in yeast is described in Bjornsti, et al., Cancer Res., 1989, 49, 6318-6323, which is disclosed in its entirety herein by reference. Bjornsti, et al., describe the complementation of conditional lethal human topoisomerase I mutant. In a similar manner, yeasts and the like can be transformed with nucleic acid molecules encoding C. albicans topoisomerase I protein that consists of SEQ ID NO:2. Accordingly, complementation can be performed with yeasts transformed with nucleic acid molecules encoding C. albicans topoisomerase I protein that consists of SEQ ID NO:2.

The methods of the invention are useful to identify selective inhibitors of C. albicans topoisomerase I protein. Inhibitors are useful as anti-fungal agents, specifically anti-C. albicans agents. Kits are provided for screening compounds for identifying selective inhibitors of C. albicans topoisomerase I protein.

The nucleotide sequence that encodes C. albicans topoisomerase I protein and that is disclosed herein as SEQ ID NO:1 allows for the production of complemented host cells which survive due to the presence of functional C. albicans topoisomerase I protein. In preparing gene constructs for complementation of deficient hosts, SEQ ID NO:1 is introduced into a host and expressed. SEQ ID NO:1 may be inserted into an expression vector in which the coding sequence is operably linked to regulatory elements required for gene expression in the host. In some preferred embodiments the expression vector is pBM272, which allows regulated expression from the GALI promoter of Saccharomyces cerevisiae. The wild-type C. albicans TOP1 coding sequence can be inserted into the BamHI and HindIII sites of pBM272. As controls, deficient host cells may be complemented with human topoisomerase I or another topoisomerase I.

The nucleotide sequence that encodes C. albicans topoisomerase I protein and that is disclosed herein as SEQ ID NO:1 allows for the production of pure C. albicans topoisomerase I protein and the design of probes which specifically hybridize to nucleic acid molecules that encode C. albicans topoisomerase I protein and antisense compounds to inhibit transcription of the gene that encodes C. albicans topoisomerase I protein.

The present invention provides substantially purified C. albicans topoisomerase I protein. The present invention provides substantially purified C. albicans topoisomerase I protein which has the amino acid sequence consisting of SEQ ID NO:2. C. albicans topoisomerase I protein can be isolated from natural sources or produced by recombinant DNA methods.

The C. albicans topoisomerase I protein sequence differs substantially from the human topoisomerase I sequence. Such differences may be used to predict which compounds might show specific binding or inhibition of the C. albicans topoisomerase I. In particular, the active site region of the C. albicans topoisomerase I has a methionine residue, Met736, instead of the leucine/isoleucine located 2 residues amino-terminal to the active site tyrosine, Tyr738, found in human and other eukaryotic topoisomerase I proteins. Antibodies may be generated and selected which specifically bind to C. albicans topoisomerase I at an epitope which includes the methionine within the active site.

Antibodies that specifically bind to C. albicans topoisomerase I protein are provided. Such ancibodies are specific inhibitors of C. albicans topoisomerase I protein and may be used in methods of isolating pure C. albicans topoisomerase I protein and methods of inhibiting C. albicans topoisomerase I protein activity.

The antibodies may be used to purify the protein from natural sources using well known techniques and readily available starting materials. Such antibodies may also be used to purify C. albicans topoisomerase I protein from material present when producing the protein by recombinant DNA methodology. The present invention relates to antibodies that bind to an epitope which is specific for C. albicans topoisomerase I protein as compared to human topoisomerase I protein. This epitope appears at amino acids 730 to 740 of SEQ ID NO:2.

As used herein, the term "antibody" is meant to refer to complete, intact antibodies, and Fab fragments and F(ab)₂ fragments thereof. Complete, intact antibodies include monoclonal antibodies such as murine monoclonal antibodies, chimeric antibodies and humanized antibodies. The antibodies specifically bind to an epitope on SEQ ID NO:2. In some preferred embodiments, that epitope appears at amino acids 730 to 740 of SEQ ID NO:2. Antibodies that bind to an epitope on SEQ ID NO:2, particularly at amino acids 730 to 740 of SEQ ID NO:2 are useful to isolate and purify C. albicans topoisomerase I protein from both natural sources or recombinant expression systems using well known techniques such as affinity chromatography. Such antibodies are useful to detect the presence of such protein in a sample and to determine if cells are expressing the protein.

The production of antibodies and the protein structures of complete, intact antibodies, Fab fragments and F(ab)₂ fragments and the organization of the genetic sequences that encode such molecules are well known and are described, for example, in Harlow, E. and D. Lane (1988) ANTIBODIES: A Laboratory Manual, Cold Spring Harbor Laboratory, Cold Spring Harbor, N.Y., which is incorporated herein by reference. Briefly, for example, the C. albicans topoisomerase I protein, or an immunogenic fragment thereof is injected into mice. The spleen of the mouse is removed, the spleen cells are isolated and fused with immortalized mouse cells. The hybrid cells, or hybridomas, are cultured and those cells which secrete antibodies are selected. The antibodies are analyzed and, if found to specifically bind to C. albicans topoisomerase I protein, the hybridoma which produces them is cultured to produce a continuous supply of antibodies.

Using standard techniques and readily available starting materials, a nucleic acid molecule that encodes C. albicans topoisomerase I protein may be isolated from a cDNA library, using probes which are designed using the nucleotide sequence information disclosed in SEQ ID NO:1. The present invention relates to an isolated nucleic acid molecule that comprises a nucleotide sequence that encodes C. albicans topoisomerase I protein and that comprises the amino acid sequence of SEQ ID NO:2. In some embodiments, the nucleic acid molecules consist of a nucleotide sequence that encodes C. albicans topoisomerase I protein. In some embodiments, the nucleic acid molecules comprise the nucleotide sequence that consists of the coding sequence in SEQ ID NO:1. In some embodiments, the nucleic acid molecules consist of the nucleotide sequence set forth in SEQ ID NO:1. The isolated nucleic acid molecules of the invention are useful to prepare constructs and recombinant expression systems for preparing isolated C. albicans topoisomerase I protein.

A genomic or cDNA library may be generated by well known techniques. Clones are identified using probes that comprise at least a portion of the nucleotide sequence disclosed in SEQ ID NO:1. The probes have at least 16 nucleotides, preferably 24 nucleotides. The probes are used to screen the genomic or cDNA libraries using standard hybridization techniques. In addition, the probes of the invention may be used to identify topoisomerase I genes from related organisms such as Aspergillus fumigatus and Cryptosporidium species.

The present invention relates to isolated nucleic acid molecules that comprise a nucleotide sequence identical or complementary to a fragment of SEQ ID NO:1 which is at least 10 nucleotides. In some embodiments, the isolated nucleic acid molecules consist of a nucleotide sequence identical or complementary to a fragment of SEQ ID NO:1 which is at least 10 nucleotides. In some embodiments, the isolated nucleic acid molecules comprise or consist of a nucleotide sequence identical or complementary to a fragment of SEQ ID NO:1 which is 15-150 nucleotides. In some embodiments, the isolated nucleic acid molecules comprise or consist of a nucleotide sequence identical or complementary to a fragment of SEQ ID NO:1 which is 15-30 nucleotides.

Isolated nucleic acid molecules that comprise or consist of a nucleotide sequence identical or complementary to a fragment of SEQ ID NO:1 which is at least 10 nucleotides are useful as probes for identifying genes and cDNA sequences that encodes C. albicans topoisomerase I protein, PCR primers for amplifying genes and cDNA that encodes C. albicans topoisomerase I protein, and antisense molecules for inhibiting transcription and translation of genes and cDNA, respectively, which encode C. albicans topoisomerase I protein.

The nucleotide sequence in SEQ ID NO:1 may be used to design probes, primers and complimentary molecules which specifically hybridize to the unique nucleotide sequences of C. albicans topoisomerase I protein. Probes, primers and complimentary molecules which specifically hybridize to nucleotide sequence that encodes C. albicans topoisomerase I protein may be designed routinely by those having ordinary skill in the art.

The present invention also includes labeled oligonucleotides which are useful as probes for performing oligonucleotide hybridization methods to identify clones that encode C. albicans topoisomerase I protein. Accordingly, the present invention includes probes that can be labelled and hybridized to unique nucleotide sequences of nucleic acid molecules that encode C. albicans topoisomerase I protein. The labelled probes of the present invention are labelled with radiolabeled nucleotides or are otherwise detectable by readily available nonradioactive detection systems. In some preferred embodiments, probes comprise oligonucleotides consisting of between 10 and 100 nucleotides. In some preferred, probes comprise oligonucleotides consisting of between 10 and 50 nucleotides. In some preferred, probes comprise oligonucleotides consisting of between 12 and 20 nucleotides. The probes preferably contain nucleotide sequence completely identical or complementary to a fragment of a unique nucleotide sequences of nucleic acid molecules that encode C. albicans topoisomerase I protein.

PCR technology is practiced routinely by those having ordinary skill in the art and its uses in diagnostics are well known and accepted. Methods for practicing PCR technology are disclosed in "PCR Protocols: A Guide to Methods and Applications", Innis, M. A., et al. Eds. Academic Press, Inc. San Diego, Calif. (1990), which is incorporated herein by reference. Applications of PCR technology are disclosed in "Polymerase Chain Reaction" Erlich, H. A., et al., Eds. Cold Spring Harbor Press, Cold Spring Harbor, N.Y. (1989), which is incorporated herein by reference. Some simple rules aid in the design of efficient primers. Typical primers are 18-28 nucleotides in length having 50% to 60% g+c composition. The entire primer is preferably complementary to the sequence it must hybridize to. Preferably, primers generate PCR products 100 base pairs to 2000 base pairs. However, it is possible to generate products of 50 base pairs to up to 10 kb and more.

PCR technology allows for the rapid generation of multiple copies of nucleotide sequences by providing 5' and 3' primers that hybridize to sequences present in a nucleic acid molecule, and further providing free nucleotides and an enzyme which fills in the complementary bases to the nucleotide sequence between the primers with the free nucleotides to produce a complementary strand of DNA. The enzyme will fill in the complementary sequences adjacent to the primers. If both the 5' primer and 3' primer hybridize to nucleotide sequences on the complementary strands of the same fragment of nucleic acid, exponential amplification of a specific double-stranded product results. If only a single primer hybridizes to the nucleic acid molecule, linear amplification produces single-stranded products of variable length.

One having ordinary skill in the art can isolate the nucleic acid molecule that encodes C. albicans topoisomerase I protein and insert it into an expression vector using standard techniques and readily available starting materials. The present invention relates to a recombinant expression vector that comprises a nucleotide sequence that encodes C. albicans topoisomerase I protein that comprises the amino acid sequence of SEQ ID NO:2. As used herein, the term "recombinant expression vector" is meant to refer to a plasmid, phage, viral particle or other vector which, when introduced into an appropriate host, contains the necessary genetic elements to direct expression of the coding sequence that encodes the C. albicans topoisomerase I protein. The coding sequence is operably linked to the necessary regulatory sequences. Expression vectors are well known and readily available. Examples of expression vectors include plasmids, phages, viral vectors and other nucleic acid molecules or nucleic acid molecule containing vehicles useful to transform host cells and facilitate expression of coding sequences. In some embodiments, the recombinant expression vector comprises the nucleotide sequence set forth in SEQ ID NO:1. The recombinant expression vectors of the invention are useful for transforming hosts to prepare recombinant expression systems for preparing the C. albicans topoisomerase I protein.

The present invention relates to a host cell that comprises the recombinant expression vector that includes a nucleotide sequence that encodes C. albicans topoisomerase I protein that comprises SEQ ID NO:2. In some embodiments, the host cell comprises a recombinant expression vector that comprises SEQ ID NO:1. Host cells for use in well known recombinant expression systems for production of proteins are well known and readily available. Examples of host cells include bacteria cells such as E. coli, yeast cells such as S. cerevisiae, insect cells such as S. frugiperda, non-human mammalian tissue culture cells chinese hamster ovary (CHO) cells and human tissue culture cells such as HeLa cells.

The present invention relates to a transgenic, non-human mammal that comprises the recombinant expression vector that comprises a nucleic acid sequence that encodes the C. albicans topoisomerase I protein that comprises the amino acid sequence of SEQ ID NO:2. Transgenic, non-human mammals useful to produce recombinant proteins are well known as are the expression vectors necessary and the techniques for generating transgenic animals. Generally, the transgenic animal comprises a recombinant expression vector in which the nucleotide sequence that encodes C. albicans topoisomerase I protein operably linked to a mammary cell specific promoter whereby the coding sequence is only expressed in mammary cells and the recombinant protein so expressed is recovered from the animal's milk:. In some embodiments, the coding sequence that encodes C. albicans topoisomerase 1 protein is SEQ ID NO:1.

In some embodiments, for example, one having ordinary skill in the art can, using well known techniques, insert such DNA molecules into a commercially available expression vector for use in well known expression systems. For example, the commercially available plasmid pSE420 (Invitrogen, San Diego, Calif.) may be used for production of C. albicans topoisomerase I in E. coli. The commercially available plasmid pYES2 (Invitrogen, San Diego, Calif.) may, for example, be used for production in S. cerevisiae strains of yeast. The commercially available MAXBAC™ complete baculovirus expression system (Invitrogen, San Diego, Calif.) may, for example, be used for production in insect cells. The commercially available plasmid pcDNA I (Invitrogen, San Diego, Calif.) may, for example, be used for production in mammalian cells such as CHO cells. One having ordinary skill in the art can use these commercial expression vectors and systems or others to produce C. albicans topoisomerase I protein using routine techniques and readily available starting materials. (See e.g., Sambrook et al., Molecular Cloning a Laboratory Manual, Second Ed. Cold Spring Harbor Press (1989), which is incorporated herein by reference.) Thus, the desired proteins can be prepared in both prokaryotic and eukaryotic systems, resulting in a spectrum of processed forms of the protein.

One having ordinary skill in the art may use other commercially available expression vectors and systems or produce vectors using well known methods and readily available starting materials. Expression systems containing the requisite control sequences, such as promoters and polyadenylation signals, and preferably enhancers, are readily available and known in the art for a variety of hosts. See e.g., Sambrook et al., Molecular Cloning a Laboratory Manual, Second Ed. Cold Spring Harbor Press (1989).

A wide variety of eukaryotic hosts are also now available for production of recombinant foreign proteins. As in bacteria, eukaryotic hosts may be transformed with expression systems which produce the desired protein directly, but more commonly signal sequences are provided to effect the secretion of the protein. Eukaryotic systems have the additional advantage that they are able to process introns which may occur in the genomic sequences encoding proteins of higher organisms. Eukaryotic systems also provide a variety of processing mechanisms which result in, for example, glycosylation, carboxy-terminal amidation, oxidation or derivatization of certain amino acid residues, conformational control, and so forth.

Commonly used eukaryotic systems include, but is not limited to, yeast, fungal cells, insect cells, mammalian cells, avian cells, and cells of higher plants. Suitable promoters are available which are compatible and operable for use in each of these host types as well as are termination sequences and enhancers, e.g. the baculovirus polyhedron promoter. As above, promoters can be either constitutive or inducible. For example, in mammalian systems, the mouse metallothionein promoter can be induced by the addition of heavy metal ions.

The particulars for the construction of expression systems suitable for desired hosts are known to those in the art. Briefly, for recombinant production of the protein, the DNA encoding the polypeptide is suitably ligated into the expression vector of choice. The DNA is operably linked to all regulatory elements which are necessary for expression of the DNA in the selected host. One having ordinary skill in the art can, using well known techniques, prepare expression vectors for recombinant production of the polypeptide.

The expression vector including the DNA that encodes C. albicans topoisomerase I protein is used to transform the compatible host which is then cultured and maintained under conditions wherein expression of the foreign DNA takes place. The protein of the present invention thus produced is recovered from the culture, either by lysing the cells or from the culture medium as appropriate and known to those in the art. One having ordinary skill in the art can, using well known techniques, isolate C. albicans topoisomerase I protein that is produced using such expression systems. The methods of purifying C. albicans topoisomerase I protein from natural sources using antibodies which specifically bind to C. albicans topoisomerase I protein as described above, may be equally applied to purifying C. albicans topoisomerase I protein produced by recombinant DNA methodology.

Examples of genetic constructs include the C. albicans topoisomerase I protein coding sequence operably linked to a promoter that is functional in the cell line into which the constructs are transfected. Examples of constitutive promoters include promoters from cytomegalovirus or SV40. Examples of inducible promoters include mouse mammary leukemia virus or metallothionein promoters. Those having ordinary skill in the art can readily produce genetic constructs useful for transfecting with cells with DNA that encodes C. albicans topoisomerase I protein from readily available starting materials. Such gene constructs are useful for the production of C. albicans topoisomerase I protein.

In some embodiments of the invention, transgenic non-human animals are generated. The transgenic animals according to the invention contain SEQ ID NO:1 under the regulatory control of a mammary specific promoter. One having ordinary skill in the art using standard techniques, such as those taught in U.S. Pat. No. 4,873,191 issued Oct. 10, 1989 to Wagner and U.S. Pat. No. 4,736,866 issued Apr. 12, 1988 to Leder, both of which are incorporated herein by reference, can produce transgenic animals which produce the C. albicans topoisomerase I protein. Preferred animals are rodents, particularly goats, rats and mice.

In addition to producing these proteins by recombinant techniques, automated peptide synthesizers may also be employed to produce C. albicans topoisomerase I protein. Such techniques are well known to those having ordinary skill in the art and are useful if derivatives which have substitutions not provided for in DNA-encoded protein production.

To screen compounds according to the methods of the present invention, at least two groups of host cells are tested. One host cell is complemented with functional C. albicans topoisomerase I. The other host cell either contains a functional endogenous topoisomerase I or is complemented with a non-C. albicans topoisomerase, preferably human topoisomerase. The groups are contacted with test compounds and the survivability of each of the two groups is observed. If a test compound leads to the death of the host cells complemented with C. albicans topoisomerase I but not those with non-C. albicans topoisomerase I, the compound is a selective inhibitor of C. albicans topoisomerase I.

In some embodiments of the invention, the preferred concentration of test compound is between 1 μM and 500 μM. A preferred concentration is 10 μM to 100 μM. In some preferred embodiments, it is desirable to use a series of dilutions of test compounds.

Kits are included which comprise containers with host cells or reagents necessary to produce host cells and/or screen test compounds. In additions, kits comprise instructions for performing such methods.

Another aspect of the present invention relates to camptothecin analogs that selectively inhibit C. albicans topoisomerase I protein, but not human topoisomerase I. According to the present invention, such compounds may be administered to individuals identified as suffering from fungal infections to kill the infecting organism.

Camptothecin analogs which selectively inhibit C. albicans topoisomerase I protein may be identified using the assay of the present invention. The host organism deficient in endogenous topoisomerase I protein is complemented with C. albicans topoisomerase I and comparative studies are performed to evaluate the effect that camptothecin analogs have on the hosts that are complemented with C. albicans topoisomerase I compared to the effect the same camptothecin analog has on the hosts with functional endogenous topoisomerase I or hosts that are complemented with non-C. albicans topoisomerase I. In some preferred, camnptothecin analogs that selectively inhibit C. albicans topoisomerase I are identified using complementation assays in which a first host cell that expresses C. albicans topoisomerase I protein to survive is contacted with a camptothecin analog and a second host cell which expresses a non-C. albicans topoisomerase I protein to survive is contacted with the same camptothecin analog. If the first host cell dies in the presence of the camptothecin analog but the second host cell lives in the presence of the same camptothecin analog, the camptothecin analog is indicated to be a selective inhibitor of C. albicans topoisomerase I protein.

The assay of the invention is useful to identify camptothecin analogs that are selective inhibitors of C. albicans topoisomerase I protein. The camptothecin analogs that are selective inhibitors are useful as anti-fungal agents, specifically anti-C. albicans agents.

In some embodiments, compounds of the invention interact with Met736.

The invention relates to camptothecin analogs that are selective inhibitors of C. albicans topoisomerase I. Camptothecin analogs that are selective inhibitors of C. albicans topoisomerase I may be identified by screening camptothecin analogs disclosed in U.S. Pat. Nos. 5,405,963; 5,401,747; 5,395,939; 5,391,745; 5,364,858; 5,342,947; 5,244,903; 5,227,380; 5,223,506; 5,212,317; 5,200,524; 5,191,082; 5,180,722; 5,162,532; 5,155,225; 5,122,606; 5,122,526; 5,106,742; 5,061,800; 5,061,795; 5,053,512; 5,041,424; 5,004,758; 4,981,968; 4,939,255; 4,914,205; 4,604,463; 4,545,880; 4,513,138; 4,473,692; 4,399,282; 4,399,276; 4,031,098; and 3,894,029; which are each incorporated herein by reference. The present invention relates to camptothecin analogs disclosed in the patents which are inhibitors of C. albicans.

In some embodiments of the invention, the preferred concentration of camptothecin analogs is between 1 μM and 500 μM. A preferred concentration is 10 μM to 100 μM. In some preferred embodiments, it is desirable to use a. series of dilutions of test compounds.

The present invention relates to methods of inhibiting C. albicans topoisomerase I activity which comprises contacting C. albicans topoisomerase I with an effective amount of a camptothecin analog with selective inhibitory activity, or its pharmaceutically acceptable salt. Camptothecin analogs that are C. albicans topoisomerase I inhibitors are useful as antifungal compounds. The present invention relates to methods of treating an animal suffering from a fungal infection by administering an amount of a C. albicans topoisomerase I with an effective amount of a camptothecin analog or analogs with selective inhibitory activity, or its pharmaceutically acceptable salt, effective to inhibit C. albicans topoisomerase I activity.

The method that is the present invention is useful in the treatment of diseases which involve funga infections such as opportunistic infections in immunocomprornised patients such as those suffering from HIV infection including those having AIDS. In addition, the methods are useful for treating vaginal yeast infections. Accordingly, the present invention relates to a method of treating a mammal suffering from a fungal infection that comprises administering to the mammal, a therapeutically effective amount of a camptothecin analog with selective inhibitory activity, or its pharmaceutically acceptable salt which inhibits C. albicans topoisomerase I. Therapeutically effective amounts of compounds used in the method that is the present invention can be formulated as pharmaceutical preparations and administered to mammals who are suffering from fungal infections in order to counter the infection.

The method that is the present invention is useful in the prevention of fungal infections such as opportunistic infections in immunocompromised patients such as those suffering from HIV infection including those having AIDS. In addition, the methods are useful for treating vaginal yeast infections. Accordingly, the present invention relates to a method of administering a prophylactically effective amount of a camptothecin analog with selective inhibitory activity, or its pharmaceutically acceptable salt which inhibits C. albicans topoisomerase I to a mammal susceptible to fungal infection. Individuals susceptible to fungal infections include immunocompromised individuals prone to opportunistic infections such as individuals suffering from HIV infection including those with AIDS or patients undergoing intensive radiation and/or chemotherapies that result in an reduction in the resistance to infection, or women undergoing therapy that includes antibiotics. A prophylactically effective dose is one in which the incidence of fungal infection is decreased upon administration of such a dose compared to the incidence of fungal infection which would occur in the absence of such a dose.

Pharmaceutically acceptable salts of these compounds may be used in practicing the methods that are the present invention. Pharmaceutical compositions containing the compounds or salts may also be used in practicing the methods that are the present invention. Pharmaceutically acceptable salts useful in the methods of that are the invention include sodium, potassium, calcium, zinc, lithium, magnesium, aluminum, diethanolamine, tromethamine, ethylenediamine, meglumine, hydrochloric, hydrobromic or acetic acid.

The present invention relates to a method of using a camptothecin analog with selective inhibitory activity, or its pharmaceutically acceptable salt which inhibits C. albicans topoisomerase I to inhibit the activity of C. albicans topoisomerase I in cells. The range of amounts of camptothecin analog with selective inhibitory activity, or its pharmaceutically acceptable salt that a cell can be exposed to and be effective for inhibiting C. albicans topoisomerase I can be determined by one having ordinary skill in the art.

By inhibiting C. albicans topoisomerase I activity, the method that is the present invention is useful in the treatment and/or prevention of fungal infections.

The mode of administration of compounds and pharmaceutical compositions according to the methods that are the invention includes any means that produces contact of the active ingredient with the infectious organism in the body of a mammal or in a body fluid or tissue. These modes of administration include but not limited to oral, topical, hypodermal, intravenous, intramuscular and intraparenteral methods of administration. In practicing the methods that are the invention, the compounds may be administered singly or in combination with other compounds used in the methods of the invention, other pharmaceutical compounds, or in conjunction with therapies. In the methods of the invention, the compounds are preferably administered with a pharmaceutically acceptable carrier selected on the basis of the selected route of administration and standard pharmaceutical practice. One camptothecin analog or a plurality of camptothecin analogs in combination may be administered.

The methods may include administration of compounds to mammals, preferably humans, in therapeutically effective amounts which are effective to inhibit C. albicans topoisomerase I and kill C. albicans. The dosage administered in any particular instance will depend upon factors such as the pharmacodynamic characteristics of the compound of the invention, its mode and route of administration; age, health, and weight of the recipient; nature and extent of symptoms; kind of concurrent treatment, frequency of treatment, and the effect desired.

It is contemplated that the daily dosage of a compound used in the methods of the invention will be in the range of from about 1 μg to about 100 mg per kg of body weight, preferably from about 1 μg to about 40 mg per kg body weight, more preferably from about 10 μg to about 20 mg per kg per day, and most preferably 10 μg to about 1 mg per kg per day. Pharmaceutical compositions may be administered in a single dosage, divided dosages or in sustained release. Persons of ordinary skill will be able to determine dosage forms and amounts with only routine experimentation based upon the considerations of this invention. Isomers of the compounds and pharmaceutical compositions, particularly optically active stereoisomers, are also within the scope of the present invention.

Compounds may be administered as pharmaceutical compositions orally in solid dosage forms, such as capsules, tablets, and powders, or in liquid dosage forms, such as elixirs, syrups, and suspensions. The compounds may also be administered parenterally in sterile liquid dosage forms or topically in a carrier. The compounds may be formulated into dosage forms according to standard practices in the field of pharmaceutical preparations. See Remington's Pharmaceutical Sciences, A. Osol, Mack Publishing Company, Easton, Pa.

Compounds may be mixed with powdered carriers, such as lactose, sucrose, mannitol, starch, cellulose derivatives, magnesium stearate, and stearic acid for insertion into gelatin capsules, or for forming into tablets. Both tablets and capsules may be manufactured as sustained release products for continuous release of medication over a period of hours. Compressed tablets can be sugar or film coated to mask any unpleasant taste and protect the tablet from the atmosphere or enteric coated for selective disintegration in the gastrointestinal tract.

Liquid dosage forms for oral administration may contain coloring and flavoring to increase patient acceptance, in addition to a pharmaceutically acceptable diluent such as water, buffer or saline solution.

For parenteral administration, a compound may be mixed with a suitable carrier or diluent such as water, a oil, saline solution, aqueous dextrose (glucose), and related sugar solutions, and glycols such as propylene glycol or polyethylene glycols. Solutions for parenteral administration contain preferably a water soluble salt of the compound. Stabilizing agents, antioxidizing agents and preservatives may also be added. Suitable antioxidizing agents include sodium bisulfite, sodium sulfite, and ascorbic acid, citric acid and its salts, and sodium EDTA. Suitable preservatives include benzalkonium chloride, methyl- or propyl-paraben, and chlorbutanol.

EXAMPLES Example 1

The topoisomerase I gene (TOP1) from Candida albicans is highly expressed in a yeast (Saccharomyces cerevisiae) strain lacking its native yeast TOP1 gene. The human TOP1 gene is highly expressed in a second top1-yeast strain. These two yeast strains are used to screen chemical compounds to find compounds which kill or inhibit the yeast expressing C. albicans TOP1 but not the yeast expressing the human TOP1.

C. albicans TOP1 was cloned using PCR. The PCR fragment was used as a probe to select a full-length TOP1 clone. The DNA sequence of the C. albicans TOP1 gene was determined and used to predict the topoisomerase I peptide sequence. The gene was excised from the DNA library vector using restriction enzymes, modified at the start of the protein-coding sequence, and ligated into a yeast expression plasmid. This plasmid is transformed into a top1⁻ yeast strain.

The C. albicans topoisomerase I protein sequence differs substantially from the human topoisomerase I sequence. Such differences may be used to predict which compounds might show specific binding or inhibition of the C. albicans topoisomerase I. In particular, the active site region has a methionine residue in place of the usual leucine/isoleucine located 2 residues amino-terminal to the active site tyrosine. Drugs may be selected based on ability to interact with this methionine residue.

It has been shown previously that overexpression of a TOP1 gene from another organism sensitizes a host yeast strain to camptothecin. Camptothecin kills such yeast strains by stabilizing a covalent topoisomerase I-DNA conjugate which leaves a broken DNA strand. The broken single strand can be processed to a double-strand break during DNA replication. If this damage is not repaired by DNA recombination, it leads to cell death.

The fastest ways to screen chemical or natural compounds or extracts, such as camptothecin analogs, for activity against C. albicans topoisomerase I is an adaption of the "zone of inhibition" assay for antibiotics. Two yeast strains, one expressing C. albicans topoisomerase I and the other strain expressing human topoisomerase I, are spread into a lawn of cells on minimal medium in 2 petri-dishes. Duplicate small paper discs are soaked in solutions of chemicals or natural products, and transferred to the surfaces of each of the 2 petri dishes. After 2-4 days at 30°, a thick lawn of yeast cells will grow on the petri-dishes. A compound, such as an active camptothecin analog, which produces a clear "zone of inhibition" of growth on the C. albicans TOP1 dish, but not the human TOP1 dish, is a specific inhibitor of C. albicans topoisomerase I.

In another embodiment of the assay, the two yeast strains, one expressing C. albicans topoisomerase I and the other expressing human topoisomerase I, are grown in liquid medium containing a possible inhibitory agent. A compound that inhibits the growth of C. albicans TOP1 yeast strain, but not the human TOP1 yeast strain, is a specific inhibitor of the C. albicans topoisomerase I.

Example 2

Yeast Transformation

The plasmid pBM-CaTOP1, and a similar plasmid expressing the human TOP1 gene, can be transformed into a top1⁻ S. cerevisiae strain by standard techniques, such as those described in Elble, R., Biotechniques, 1992, 13 (1), 78-80, which is disclosed in its entirety herein by reference. The plasmid can be selected by growing the yeast strain in minimal medium lacking uracil. The URA3 gene within pBM-CaTOP1 will enable the yeast strain to grow on medium lacking uracil. The expression of C. albicans topoisomerase I in S. cerevisiae can be verified by assaying the ability of a crude extract of this yeast strain to remove plasmid DNA supercoils as detailed in Thrash, et al., Proc. Natl. Acad. Sci. USA, 1985, 82, 4374-4378, which is disclosed in its entirety herein by reference.

Cloning C. albicans TOP1 Gene Into Expression Vector pBM272

The native genomic C. albicans TOP1 clone pCaT1-R12 constitutes a 3.4 kb EcoRI-EcoRI fragment containing the entire TOP1 gene, ligated into the pBC SK(-) plasmid (Stratagene, La Jolla, Calif.). This gene was modified by introducing a BamHI restriction site immediately 5' upstream of the coding sequence using standard techniques (Sambrook, et al., Molecular Cloning a Laboratory Manual, Second Ed. Cold Spring Harbor Press (1989)). The entire gene coding sequence was excised as a 2.4 kb BamHI-HindIII DNA fragment, and ligated into the BamHI-HindIII sites of yeast expression vector pBM272 using standard techniques. This plasmid, pBM-CaTOP1, can be introduced into top1⁻ yeast strain L1242 (S. cerevisiae; Thrash, et al., Proc. Natl. Acad. Sci. USA, 1985, 82, 4374-4378) or a derivative strain, K2979, provided by Dr. Ralph Keil, Hershey Medical Center, Hershey, Pa.). The K2979 genotype is: MATa HindIII(top1::LEU2) his4-260 ade2-1 ura3-52 leu2-3,112 trp1-HIII can1^(R) lys2ΔBX::CAN1::LYS2 rDNA::URA3 rDNA::ADE2.

The cloned genomic C. albicans TOP1 gene can also be used to generate a top1⁻ /top1⁻ C. albicans strain using the gene for gene disruption using standard techniques known to fungal geneticists.

Example 3

Camptothecin analogs may have the formula: ##STR1## wherein: R is a lower alkyl;

R₁ is H, lower alkyl, lower alkoxy, or halo; and

R₂, R₃, R₄ and R₅ may each independently be H, amino hydroxy, lower alkyl, lower alkoxy, lower alkylthio, di(lower alkyl)amino, cyano, methylenedioxy, Formyl, nitro, halo, trifluoromethyl, aminomethyl, azido, amido, hydrazino, or any of the standard twenty amino acids bonded to the A ring via the amino-nitrogen atom.

The synthesis of camptothecin analogs with this formula can be carried out by those having ordinary skill in the art using synthesis schemes such as those that are described in U.S. Pat. Nos. 5,212,317, 5,191,082, 5,395,939, 5,162,532, and 5,200,524.

Example 4

Camptothecin analogs may have the formula: ##STR2## wherein: R₁ is H, halo, or an alkyl group with 1-4 carbons; and

X is a chlorine atom or --NR₂ R₃ where R₂ and R₃ are the same or different and each represents a hydrogen, a substituted or unsubstituted alkyl group with 1-4 carbons, or a substituted or unsubstituted carbocyclic or heterocyclic group.

The synthesis of Camptothecin analogs with this formula can be carried out by those having ordinary skill in the art using synthesis schemes such as those that are described in U.S. Pat. No. 4,604,463.

Example 5

Camptothecin analogs may have the formula: ##STR3## wherein: R₁ is H, alkyl, hydroxyl, CH₂ OH, COOH, aralkyl, alkoxy, acyloxy, CH₂ OR₄, COOR₅ wherein R₄ is an alkyl or acyl group and R₅ is a lower alkyl or acyl group;

R₂ is H, alkyl, aralkyl, hydroxymethyl, carboxymethyl, acyloxymethyl, --CHO, --CH₂ OR', --CH(OR')₂ or --CH═N--X where R' is a lower alkyl group with 1-6 carbons or a phenylalkyl group with 1-3 carbon in the alkylene moiety thereof and X is hydroxyl or --NR₆ R₇ where R₆ and R₇ are the same or different and each represents a hydrogen, or an alkyl group with 1-6 carbons, or when R₆ is hydrogen, R₇ may be an alkyl group with 1-6 carbons, a substituted or unsubstituted aryl group, a carbamoyl group, an acyl group, an aminoalkyl group or an amido group or when R₆ is a lower alkyl group R₇ may be an aminoalkyl group or R₆ and R₇ may be combined together with a nitrogen to form a heterocycle or quaternary salt thereof;

R₃ is the grouping --XR' where R' is H, alkyl, or acyl and X is oxygen or sulphur, a nitro group, an amino group, an alkylamino group, an acylamino group, or a halogen; and

Z is hydrogen or an acyl group.

The synthesis of camptothecin analogs with this formula can be carried out by those having ordinary skill in the art using synthesis schemes such as those that are described in U.S. Pat. Nos. 4,473,692, 4,545,880, 4,399,276, 4,399,282.

Example 6

Camptothecin analogs may be camptothecirl oxide derivatives which have the formula as shown in Example 5 except that the Nitrogen on ring b is substituted with an oxygen.

The synthesis of camptothecin oxide derivatives with this formula can be carried out by those having ordinary skill in the art using synthesis schemes such as those that are described in U.S. Pat. No. 4,513,138.

Example 7

Camptothecin analogs may have the formula: ##STR4## wherein ring a is substituted by R_(n). Substituents include hydroxy, nitro, amino, chloro, bromo, iodo, fluoro, C₁₋₈ alkyl, C₁₋₈ alkoxy, trifluoromethyl, amino methyl, amido, hydrazino, azido, formyl,and cyano groups as well as groups comprising amino acids bonded to the A ring via the amino-nitrogen atom. Preferred alkyl groups include methyl, ethyl, propyl, butyl, isopropyl, isbutyl and secbutyl groups. Preferred alkoxy groups include methoxy, ethoxy, propoxy, and isopropoxy groups. Preferred amino acids are the the standard twenty amino acids. Two substituents on the a ring may be joined together to form a bifunction substituent. In addition, ring a may be modified to contain a hetero atom. Ring a may be a five or six carbon ring with an oxygen, nitrogen or sulphur.

The synthesis of camptothecin analogs with this formula can be carried out by those having ordinary skill in the art using synthesis schemes such as those that are described in U.S. Pat. Nos. 5,106,742, 5,122,526, 4,981,968, 5,180,722, 5,401,747, 5,227,380, 5,364,858, 5,244,903.

Example 8

Camptothecin analogs which have the formula as shown in Example 7 may be further substituted at the carbon on ring b ortho to the nitrogen on ring b. The position may substituted with a C₁₋₈ alkyl.

The synthesis of camptothecin analogs with this formula can be carried out by those having ordinary skill in the art using synthesis schemes such as those that are described in U.S. Pat. Nos. 5,122,606 and 5,053,512.

Example 9

Camptothecin analogs may have the formula: ##STR5## wherein: E is H, CO₂ R, CONH₂, CONHR, CONR₂, acyl, or CN;

X is H, OH, or OR;

R₁, R₂, R₃, and R₄ are independently the same or different and are H, or a linear or branched chain alkyl, alkylaryl, hydroxyalkyl group, or an aryl group, and R₁ may be allyl, propargyl or benzyl;

R₅, R₆, R₇, R₈, and R₉, are independently the same or different and are H, or a linear or branched chain alkyl, alkylaryl, alkoxy, hydroxyalkyl group, or aminoalkoxy group, or an aryl or aryloxy group, or an amino, lower acylamino, di(lower alkyl)amino group, or a C-glycal or hydroxyl, CO₂ R, nitro, cyano, Cl, F, Br, I, SR₁₀, NR₁₁ R₁₂ or OR₁₃, or R₆ is CHO, CH₂ R₁₄ and R₇ is H, hydroxy, --CH₂ NH₂ or formyl;

R is H, or a linear or branched alkyl, alkylaryl, or hydroxyalkyl group, or an aryl group,

R₁₀, R₁₁, and R₁₂, are independently the same or different and are H, or a linear or branched chain alkyl, alkylaryl, hydroxyalkyl, or acyl group, or an aryl group;

R₁₃ is glycosyl;

R₁₄ is OR₁₅, SR₁₅, CH₂ NH₂, cyano, NR₁₅ R₁₆, or N⁺ R₁₅ R_(l6) R₁₇ !;

R₁₅, R₁₆ and R₁₇ are the same or different and are selected from H, C₁₋₆ alkyl, C₂₋₆ hydroxyalkyl, C₁₋₆ dialkylamino-C₂₋₆ alkyl, C₁₋₆ alkylamino-C₂₋₆ alkyl, C₂₋₆ aminoalkyl or a 3-7 member unsubstituted carbocyclic ring; and

n is 0 or 1.

The synthesis of camptothecin analogs with this formula can be carried out by those having ordinary skill in the art using synthesis schemes such as those that are described in U.S. Pat. Nos. 5,391,745, 5,061,800, 5,004,758, 4,031,098, and 3,894,029.

Example 10

Camptothecin analogs may have the formula: ##STR6## wherein: n is 1 or 2;

R₁ is independently, H, lower alkyl, (C₃₋₇)cycloalkyl lower alkyl, lower alkenyl, hydroxy lower alkyl, lower alkoxy lower alkyl; and

R₂ is H or a pharmaceutically acceptable salt.

The synthesis of camptothecin analogs with this formula can be carried out by those having ordinary skill in the art using synthesis schemes such as those that are described in U.S. Pat. No. 5,342,947.

Example 11

Camptothecin analogs may have the formula: ##STR7## wherein: n is 1 or 2;

R₁ and R₂ are, independently, hydrogen atoms, hydroxyl groups, C₁₋₆ alkyl groups, C₁₋₆ alkenyl groups, C₁₋₆ alkynyl groups, C₁₋₆ alkoxyl groups, C₁₋₆ aminoalkoxyl groups, halogen atoms, nitro groups, cyano groups, mercapto groups, C₁₋₆ alkylthio groups, C₁₋₆ hydroxyalkyl groups, C₁₋₆ halogenoalkyl groups, C₁₋₆ cyanoalkyl groups, C₁₋₆ nitroalkyl groups, amino groups which may contain protective groups, C₁₋₆ aminoalkyl groups which may contain protective groups or C₁₋₆ alkyl groups which may contain protective groups or C₁₋₆ alkyl groups, C₁₋₆ aminoalkylamino groups which may contain protective groups or C₁₋₆ alkyl groups at the amino-position, heterocyclic C₁₋₆ alkyl groups which may contain C₁₋₆ alkyl, C₁₋₆ alkoxyl, amino, halogeno, nitro, or cyano groups, heterocyclic C₁₋₆ alkylamino groups which may contain C₁₋₆ alkyl, C₁₋₆ alkoxyl, amino (which may contain protective groups), halogeno, nitro, cyano groups, or protective groups, amino-heterocyclic groups which may contain protective groups or C₁₋₆ alkyl groups at the nitrogen atom of the heterocyclic ring moiety or amino position, heterocyclic-amino groups which may contain protective groups of C₁₋₆ alkyl groups at the nitrogen atom of the heterocyclic ring moiety or amino position, carbamoyl groups which may contain protective groups or C₁₋₆ alkyl groups, heterocyclic carbonyl groups which may contain C₁₋₆ alkyl, C₁₋₆ alkoxyl, amino, hydroxyl, halogeno, nitro, or cyano groups;

R₃ represents an C₁₋₆ alkyl group;

Z represents O.S. CH--R₄ (R₄ stands for a hydrogen atom or a C₁₋₆ alkyl group), or N--R₅ (R₅ stands for a hydrogen atom, a C₁₋₆ alkyl group, or a protective group for the amino group); and

m and n independently represent 0, 1 or 2 provided that m and n are not both equal to 2, and wherein said heterocyclic group is selected from the group consisting of azetidine, pyrrolidine, piperidine, piperazine, imidazoline, and morpholine, and wherein said protective group is selected from the group consisting of acetyl, formyl, trityl, terbutoxycarbonyl, and p-methoxybenzoyloxycarbonyl.

The synthesis of camptothecin analogs with this formula can be carried out by those having ordinary skill in the art using synthesis schemes such as those that are described in U.S. Pat. Nos. 4,939,255 and 5,062,795.

Example 12

Camptothecin analogs may have the formula: ##STR8## wherein the compound is 8-methyl-7-(1-oxopropyl)indolizino 1,2-b!quinolin-9(11H)-one or a substituted 8-methyl-7-(1-oxopropyl)indolizino 1,2-b!quinolin-9(11H)-one.

The synthesis of camptothecin analogs with this formula can be carried out by those having ordinary skill in the art using synthesis schemes such as those that are described in U.S. Pat. No. 5,155,225.

Example 13

Camptothecin analogs may have the formula: ##STR9## wherein: X is a lower alkyl group; and

R is a hydrogen atom or the grouping --COY where Y is a linear or branched unsubstituted C₁ -C₁ alkyl group, a lower alkyl group substituted by a halogen atom or a lower alkylthio, amino, acylamino, hydroxyl, lower alkoxy, arloxy or lower alkoxycarbonyl group; a C₃ -C₁₉ alkenyl, C₃ -C₁₉ alkynyl or C₃ -C₈ cycloalkyl group; a C₃ -C₈ cycloalkyl group substituted by an acylamino-lower alkyl group; an N-acylpyrrolidyl group, a phenyl group; a phenyl group substituted by a halogen atom or a trifluoromethyl, nitro, amino, lower alkoxycarbonyl, lower alkyl, phenyl or lower alkoxy; a cinnamyl group; a benzyl group; a naphthyl group; a pyridyl group; a furyl group; or a thienyl group, as well as acid addition salts and quaternary ammonium salts thereof.

The synthesis of camptothecin analogs with this formula can be carried out by those having ordinary skill in the art using synthesis schemes such as those that are described in U.S. Pat. No. 4,914,205.

    __________________________________________________________________________     #             SEQUENCE LISTING                                                 - (1) GENERAL INFORMATION:                                                     -    (iii) NUMBER OF SEQUENCES: 2                                              - (2) INFORMATION FOR SEQ ID NO:1:                                             -      (i) SEQUENCE CHARACTERISTICS:                                           #pairs    (A) LENGTH: 3143 base                                                          (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: double                                                       (D) TOPOLOGY: unknown                                                -     (ii) MOLECULE TYPE: genomic DNA                                          -     (ix) FEATURE:                                                                      (A) NAME/KEY: CDS                                                              (B) LOCATION: 547..2889                                              #ID NO:1: (xi) SEQUENCE DESCRIPTION: SEQ                                       - GAATTCCTCA AACACGGTCA AAAAAATACC AACTATCTTC TGTTTCTCCC CA - #CTCACACG          60                                                                           - ACCCAACTAT TTTTTTGGTG ATGGTTTTAG GCGCGACGTT AATCATTTTT AC - #TATTGAGA         120                                                                           - ATGATTACTC CCACATTCTA TTACACCTCA TCTTCATCTT CATCTTTCAT CT - #TTCACATC         180                                                                           - ACTAAATATA ACCTTGCGAC CTTCACAAAT TTTTTTTTTT GACAAGCAAT CC - #AAAATTAC         240                                                                           - AATTTTCATT TCATTTCTTT TATATATAAA AGTTTTTCAC CATTAATTTC AC - #CACACATC         300                                                                           - TCATTAGCAA TTGGGCAAAA ATAGAAAGTA ATTTTATAAC TTATAACCAA AA - #ACAATTCA         360                                                                           - AGAACAATAT CATTATTATT AAATTTATCA CGGAATTTGT TTTGCAAATC AA - #GTAAGAAC         420                                                                           - AATTTCCATC AATTTACTCA TCAGTTTGGT TGTAATAATA AAAACAGATT AT - #TTTTCTTA         480                                                                           - TCATCACCAC CAAGAGTATT CCGTTATTTA AATCCATTAT TTGTTCGTTC AT - #ATAGCATA         540                                                                           #GCC TTG TCT AGA CTC       588AA GAA GAC ATT                                          Met Ser Ser Ser Asp Glu Gl - #u Asp Ile Ala Leu Ser Arg Leu             #      10                                                                      - GCT AAA AAA TCA TCC TCG ATC ACT TCA GCT TC - #C ACT TAT GAA GAC GAT           636                                                                           Ala Lys Lys Ser Ser Ser Ile Thr Ser Ala Se - #r Thr Tyr Glu Asp Asp            # 30                                                                           - GAA GAT GAT GAT ATC CCT TTA GCT AAA AAA TC - #C AGG AAA AAG AGG GTT           684                                                                           Glu Asp Asp Asp Ile Pro Leu Ala Lys Lys Se - #r Arg Lys Lys Arg Val            #                 45                                                           - GAA TCT GAT TAT GAA GAA GAT GAA GAC GAA GT - #C CCA TTG AAA AAG AGA           732                                                                           Glu Ser Asp Tyr Glu Glu Asp Glu Asp Glu Va - #l Pro Leu Lys Lys Arg            #             60                                                               - AAA TTG TCT AAT GGT AGA GCA AAA AAA CAA GT - #T AAA ACC GAA ACT AAA           780                                                                           Lys Leu Ser Asn Gly Arg Ala Lys Lys Gln Va - #l Lys Thr Glu Thr Lys            #         75                                                                   - GTT AAA AAG GAA CCT AAA AGT GCC AAT AAA TC - #C AAA TCT ACA TCT AAA           828                                                                           Val Lys Lys Glu Pro Lys Ser Ala Asn Lys Se - #r Lys Ser Thr Ser Lys            #     90                                                                       - AAG GAC ACC AAA GTT AAG AAA GAG AAA ACT AC - #A GTC AAG AAG GAA TCT           876                                                                           Lys Asp Thr Lys Val Lys Lys Glu Lys Thr Th - #r Val Lys Lys Glu Ser            #110                                                                           - AAA GCC ACA AGC ACT AAA GTG AAA GAA GAA TC - #C AAA ACT CAA TCA GAT           924                                                                           Lys Ala Thr Ser Thr Lys Val Lys Glu Glu Se - #r Lys Thr Gln Ser Asp            #               125                                                            - TCA CAA GCA TCG GTT AAA TCT GAA ACT CCT GA - #A GAA GAT CAA GGG TAC           972                                                                           Ser Gln Ala Ser Val Lys Ser Glu Thr Pro Gl - #u Glu Asp Gln Gly Tyr            #           140                                                                - AAA TGG TGG GAA GTG AAT CAA GAA GAA GAA GG - #T GAT GGT TAT ATC AAA          1020                                                                           Lys Trp Trp Glu Val Asn Gln Glu Glu Glu Gl - #y Asp Gly Tyr Ile Lys            #       155                                                                    - TGG CAA ACA CTA GAA CAT AAC GGT GTT ATG TT - #T CCA CCA CCA TAT GAA          1068                                                                           Trp Gln Thr Leu Glu His Asn Gly Val Met Ph - #e Pro Pro Pro Tyr Glu            #   170                                                                        - CCA TTA CCA TCT CAT GTC AAA TTA TAT TAT AA - #C AAT AAA CCA GTT AAT          1116                                                                           Pro Leu Pro Ser His Val Lys Leu Tyr Tyr As - #n Asn Lys Pro Val Asn            175                 1 - #80                 1 - #85                 1 -        #90                                                                            - TTA CCT CCA GAA GCA GAA GAA GTT GCC GGA TT - #T TAT GGA GCA ATG TTA          1164                                                                           Leu Pro Pro Glu Ala Glu Glu Val Ala Gly Ph - #e Tyr Gly Ala Met Leu            #               205                                                            - GAA ACT GAT CAT GCT AAA AAC CCA GTT TTC CA - #A AAG AAT TTT TTC AAT          1212                                                                           Glu Thr Asp His Ala Lys Asn Pro Val Phe Gl - #n Lys Asn Phe Phe Asn            #           220                                                                - GAT TTT TTG GAA GTT TTA AAA GAA TGT GGT GG - #T TGT GGT GTT GAA ATT          1260                                                                           Asp Phe Leu Glu Val Leu Lys Glu Cys Gly Gl - #y Cys Gly Val Glu Ile            #       235                                                                    - AAA AAA TTT GAA AAA TTA GAT TTT AGT AAA AT - #G TAT GCT CAT TTT GAA          1308                                                                           Lys Lys Phe Glu Lys Leu Asp Phe Ser Lys Me - #t Tyr Ala His Phe Glu            #   250                                                                        - AAA TTA CGT GAA GAG AAA AAG GCC ATG AGT AG - #G GAA GAA AAG AAA AGA          1356                                                                           Lys Leu Arg Glu Glu Lys Lys Ala Met Ser Ar - #g Glu Glu Lys Lys Arg            255                 2 - #60                 2 - #65                 2 -        #70                                                                            - ATC AAA GAA GAA AAA GAA AAA GAA GAA GAA CC - #T TAT AGG ACT TGT TAT          1404                                                                           Ile Lys Glu Glu Lys Glu Lys Glu Glu Glu Pr - #o Tyr Arg Thr Cys Tyr            #               285                                                            - CTT AAT GGT AGA AAA GAA TTA GTG GGG AAT TT - #C CGT ATT GAA CCT CCA          1452                                                                           Leu Asn Gly Arg Lys Glu Leu Val Gly Asn Ph - #e Arg Ile Glu Pro Pro            #           300                                                                - GGT TTA TTC CGT GGT CGT GGT GCA CAT CCT AA - #A ACT GGG AAA TTA AAA          1500                                                                           Gly Leu Phe Arg Gly Arg Gly Ala His Pro Ly - #s Thr Gly Lys Leu Lys            #       315                                                                    - CGT CGA GTA GTG CTG GAA CAA GTG ACT TTG AA - #T TTA GGT AAA GAT GCT          1548                                                                           Arg Arg Val Val Leu Glu Gln Val Thr Leu As - #n Leu Gly Lys Asp Ala            #   330                                                                        - AAA ATA CCT GAA CCA CCT GCA GGC CAT CAA TG - #G GGG GAA ATT AGA CAT          1596                                                                           Lys Ile Pro Glu Pro Pro Ala Gly His Gln Tr - #p Gly Glu Ile Arg His            335                 3 - #40                 3 - #45                 3 -        #50                                                                            - GAT AAT GAA GTC ACT TGG TTA GCC ATG TGG AA - #A GAA AAT ATT TCT GAT          1644                                                                           Asp Asn Glu Val Thr Trp Leu Ala Met Trp Ly - #s Glu Asn Ile Ser Asp            #               365                                                            - TCA TTG AAA TAC GTT AGA TTT GCT AAT AAT TC - #T TCA GTT AAA GGT CAA          1692                                                                           Ser Leu Lys Tyr Val Arg Phe Ala Asn Asn Se - #r Ser Val Lys Gly Gln            #           380                                                                - TCC GAT TTC AAA AAA TTT GAA ACG GCG AGA AA - #A TTA AGA GAT CAC GTT          1740                                                                           Ser Asp Phe Lys Lys Phe Glu Thr Ala Arg Ly - #s Leu Arg Asp His Val            #       395                                                                    - GAT TCT ATT AGA AAA GAT TAT ACC AAA ATG TT - #A AAA TCA GAG AAA ATG          1788                                                                           Asp Ser Ile Arg Lys Asp Tyr Thr Lys Met Le - #u Lys Ser Glu Lys Met            #   410                                                                        - CAA GAT AGA CAA ATG GCC ACG GCT ATG TAT CT - #T ATT GAT GTT TTT GCA          1836                                                                           Gln Asp Arg Gln Met Ala Thr Ala Met Tyr Le - #u Ile Asp Val Phe Ala            415                 4 - #20                 4 - #25                 4 -        #30                                                                            - TTG AGG GCT GGT GGT GAA AAA GGT GAG GAT GA - #A GCC GAT ACC GTT GGT          1884                                                                           Leu Arg Ala Gly Gly Glu Lys Gly Glu Asp Gl - #u Ala Asp Thr Val Gly            #               445                                                            - TGT TGT TCA TTA CGA TAT GAA CAT GTA ACT TT - #A AAA CCA CCC AAC AAG          1932                                                                           Cys Cys Ser Leu Arg Tyr Glu His Val Thr Le - #u Lys Pro Pro Asn Lys            #           460                                                                - GTT ATT TTC GAT TTT TTG GGT AAA GAT TCA AT - #T AGA TTT TAT CAA GAA          1980                                                                           Val Ile Phe Asp Phe Leu Gly Lys Asp Ser Il - #e Arg Phe Tyr Gln Glu            #       475                                                                    - GTT GAA GTT GAT AAA CAA GTT TTC AAA AAT CT - #A CGA ATT TTC AAA AAA          2028                                                                           Val Glu Val Asp Lys Gln Val Phe Lys Asn Le - #u Arg Ile Phe Lys Lys            #   490                                                                        - TCT CCT AAA CAA CCT GGT GAT GAT TTA TTT GA - #T CGT ATA AAC CCT TCA          2076                                                                           Ser Pro Lys Gln Pro Gly Asp Asp Leu Phe As - #p Arg Ile Asn Pro Ser            495                 5 - #00                 5 - #05                 5 -        #10                                                                            - TTA GTC AAT CGA CAA TTA CAA AAT TAT ATG AA - #A GGA TTA ACA GCA AAA          2124                                                                           Leu Val Asn Arg Gln Leu Gln Asn Tyr Met Ly - #s Gly Leu Thr Ala Lys            #               525                                                            - GTT TTC CGT ACA TAT AAT GCC TCG AAA ACC AT - #G CAA GAT CAA ATT GAT          2172                                                                           Val Phe Arg Thr Tyr Asn Ala Ser Lys Thr Me - #t Gln Asp Gln Ile Asp            #           540                                                                - ATA ATT GAA AAT GAA GGT ACA GTG GCG GAA AA - #A GTG GCT AAA TTC AAT          2220                                                                           Ile Ile Glu Asn Glu Gly Thr Val Ala Glu Ly - #s Val Ala Lys Phe Asn            #       555                                                                    - GCT GCC AAT AGA ACG GTG GCT ATT TTA TGT AA - #T CAC CAG CGT ACG GTC          2268                                                                           Ala Ala Asn Arg Thr Val Ala Ile Leu Cys As - #n His Gln Arg Thr Val            #   570                                                                        - AGT AAA ACC CAT GGT GAT AGT GTT CAG AGA AT - #T AAT GAC AAA TTG AAA          2316                                                                           Ser Lys Thr His Gly Asp Ser Val Gln Arg Il - #e Asn Asp Lys Leu Lys            575                 5 - #80                 5 - #85                 5 -        #90                                                                            - AAA TTC ATG TGG CAA AAG ATT AGA TTA AAG AA - #A ATG ATC TTA CAA TTA          2364                                                                           Lys Phe Met Trp Gln Lys Ile Arg Leu Lys Ly - #s Met Ile Leu Gln Leu            #               605                                                            - GAA CCC AAA TTG AAA AAG AAA GAT TCG AAA TA - #T TTT GAA GAA ATT GAT          2412                                                                           Glu Pro Lys Leu Lys Lys Lys Asp Ser Lys Ty - #r Phe Glu Glu Ile Asp            #           620                                                                - GAT TTA CTC AAA GAA GAT ATT GAA CAT ATT CA - #T CAT ACT ATA ATT AAA          2460                                                                           Asp Leu Leu Lys Glu Asp Ile Glu His Ile Hi - #s His Thr Ile Ile Lys            #       635                                                                    - AGA CAA CGA GAA CAA GCT AAA AAA AAA TTA GA - #A CGT GAT AAT GAA AAA          2508                                                                           Arg Gln Arg Glu Gln Ala Lys Lys Lys Leu Gl - #u Arg Asp Asn Glu Lys            #   650                                                                        - TTG AAA CTT GAA GGT AAA CCA TTA TTA ACT GA - #A TCA GAT ATA AAA GAT          2556                                                                           Leu Lys Leu Glu Gly Lys Pro Leu Leu Thr Gl - #u Ser Asp Ile Lys Asp            655                 6 - #60                 6 - #65                 6 -        #70                                                                            - AAA TTA GAT AAA ATT GAT GAA TTA GAA AAA GA - #A TAT CAA AAA GAA TTG          2604                                                                           Lys Leu Asp Lys Ile Asp Glu Leu Glu Lys Gl - #u Tyr Gln Lys Glu Leu            #               685                                                            - AAA ACT GGT AAA CCA ATA GTC ACC AAA AAT GC - #T ACC GTT GAA AAA TTA          2652                                                                           Lys Thr Gly Lys Pro Ile Val Thr Lys Asn Al - #a Thr Val Glu Lys Leu            #           700                                                                - AAA CAA CAA ATT GAA ACT CTT GAA AAT AAA AT - #T CTT AAT GTT TCA ATT          2700                                                                           Lys Gln Gln Ile Glu Thr Leu Glu Asn Lys Il - #e Leu Asn Val Ser Ile            #       715                                                                    - CAA TTA AAA GAT AAA GAA GAT AAT TCT GAA GT - #T TCT TTA GGA ACT TCA          2748                                                                           Gln Leu Lys Asp Lys Glu Asp Asn Ser Glu Va - #l Ser Leu Gly Thr Ser            #   730                                                                        - AAA ATG AAT TAT ATT GAT CCA AGA TTA ATT GT - #T ATG TTT TCT AAA AAA          2796                                                                           Lys Met Asn Tyr Ile Asp Pro Arg Leu Ile Va - #l Met Phe Ser Lys Lys            735                 7 - #40                 7 - #45                 7 -        #50                                                                            - TTT GAT GTT CCT ATT GAA AAA TTA TTT ACC AA - #A ACT TTA AGA GAA AAG          2844                                                                           Phe Asp Val Pro Ile Glu Lys Leu Phe Thr Ly - #s Thr Leu Arg Glu Lys            #               765                                                            - TTC ATT TGG GCT ATT GAA TCA GCT GAT GAA AA - #T TGG AGA TTC TAA              2889                                                                           Phe Ile Trp Ala Ile Glu Ser Ala Asp Glu As - #n Trp Arg Phe  *                 #           780                                                                - AATTAGGGGT TTGTTTCTTA GCTTATTATT ATATACTATA TGCTGTAGAG TA - #AAATTTTG        2949                                                                           - TACCTTGTAA TATATATATA TACATTGTTT CAACATAGAA AAATAGATTG AT - #ACTGCAGT        3009                                                                           - ATGAAAAAGA ATATGCACAC ACCAAGCAAG TGTATTTTAG ATAAAGGATT GG - #TGTTTTGA        3069                                                                           - TATTGGAAGG GTGAAAGATG AAGGGGGTAT CACACAGACA CGTACAATCA AG - #AAATTGAA        3129                                                                           #   3143                                                                       - (2) INFORMATION FOR SEQ ID NO:2:                                             -      (i) SEQUENCE CHARACTERISTICS:                                                     (A) LENGTH:  780 ami - #no acids                                               (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                 -     (ii) MOLECULE TYPE: protein                                              -           (xi) SEQUENCE DESCRIPTION: - # SEQ ID NO:2:                        - Met Ser Ser Ser Asp Glu Glu Asp Ile Ala Le - #u Ser Arg Leu Ala Lys          #                 15                                                           - Lys Ser Ser Ser Ile Thr Ser Ala Ser Thr Ty - #r Glu Asp Asp Glu Asp          #             30                                                               - Asp Asp Ile Pro Leu Ala Lys Lys Ser Arg Ly - #s Lys Arg Val Glu Ser          #         45                                                                   - Asp Tyr Glu Glu Asp Glu Asp Glu Val Pro Le - #u Lys Lys Arg Lys Leu          #     60                                                                       - Ser Asn Gly Arg Ala Lys Lys Gln Val Lys Th - #r Glu Thr Lys Val Lys          # 80                                                                           - Lys Glu Pro Lys Ser Ala Asn Lys Ser Lys Se - #r Thr Ser Lys Lys Asp          #                 95                                                           - Thr Lys Val Lys Lys Glu Lys Thr Thr Val Ly - #s Lys Glu Ser Lys Ala          #           110                                                                - Thr Ser Thr Lys Val Lys Glu Glu Ser Lys Th - #r Gln Ser Asp Ser Gln          #       125                                                                    - Ala Ser Val Lys Ser Glu Thr Pro Glu Glu As - #p Gln Gly Tyr Lys Trp          #   140                                                                        - Trp Glu Val Asn Gln Glu Glu Glu Gly Asp Gl - #y Tyr Ile Lys Trp Gln          145                 1 - #50                 1 - #55                 1 -        #60                                                                            - Thr Leu Glu His Asn Gly Val Met Phe Pro Pr - #o Pro Tyr Glu Pro Leu          #               175                                                            - Pro Ser His Val Lys Leu Tyr Tyr Asn Asn Ly - #s Pro Val Asn Leu Pro          #           190                                                                - Pro Glu Ala Glu Glu Val Ala Gly Phe Tyr Gl - #y Ala Met Leu Glu Thr          #       205                                                                    - Asp His Ala Lys Asn Pro Val Phe Gln Lys As - #n Phe Phe Asn Asp Phe          #   220                                                                        - Leu Glu Val Leu Lys Glu Cys Gly Gly Cys Gl - #y Val Glu Ile Lys Lys          225                 2 - #30                 2 - #35                 2 -        #40                                                                            - Phe Glu Lys Leu Asp Phe Ser Lys Met Tyr Al - #a His Phe Glu Lys Leu          #               255                                                            - Arg Glu Glu Lys Lys Ala Met Ser Arg Glu Gl - #u Lys Lys Arg Ile Lys          #           270                                                                - Glu Glu Lys Glu Lys Glu Glu Glu Pro Tyr Ar - #g Thr Cys Tyr Leu Asn          #       285                                                                    - Gly Arg Lys Glu Leu Val Gly Asn Phe Arg Il - #e Glu Pro Pro Gly Leu          #   300                                                                        - Phe Arg Gly Arg Gly Ala His Pro Lys Thr Gl - #y Lys Leu Lys Arg Arg          305                 3 - #10                 3 - #15                 3 -        #20                                                                            - Val Val Leu Glu Gln Val Thr Leu Asn Leu Gl - #y Lys Asp Ala Lys Ile          #               335                                                            - Pro Glu Pro Pro Ala Gly His Gln Trp Gly Gl - #u Ile Arg His Asp Asn          #           350                                                                - Glu Val Thr Trp Leu Ala Met Trp Lys Glu As - #n Ile Ser Asp Ser Leu          #       365                                                                    - Lys Tyr Val Arg Phe Ala Asn Asn Ser Ser Va - #l Lys Gly Gln Ser Asp          #   380                                                                        - Phe Lys Lys Phe Glu Thr Ala Arg Lys Leu Ar - #g Asp His Val Asp Ser          385                 3 - #90                 3 - #95                 4 -        #00                                                                            - Ile Arg Lys Asp Tyr Thr Lys Met Leu Lys Se - #r Glu Lys Met Gln Asp          #               415                                                            - Arg Gln Met Ala Thr Ala Met Tyr Leu Ile As - #p Val Phe Ala Leu Arg          #           430                                                                - Ala Gly Gly Glu Lys Gly Glu Asp Glu Ala As - #p Thr Val Gly Cys Cys          #       445                                                                    - Ser Leu Arg Tyr Glu His Val Thr Leu Lys Pr - #o Pro Asn Lys Val Ile          #   460                                                                        - Phe Asp Phe Leu Gly Lys Asp Ser Ile Arg Ph - #e Tyr Gln Glu Val Glu          465                 4 - #70                 4 - #75                 4 -        #80                                                                            - Val Asp Lys Gln Val Phe Lys Asn Leu Arg Il - #e Phe Lys Lys Ser Pro          #               495                                                            - Lys Gln Pro Gly Asp Asp Leu Phe Asp Arg Il - #e Asn Pro Ser Leu Val          #           510                                                                - Asn Arg Gln Leu Gln Asn Tyr Met Lys Gly Le - #u Thr Ala Lys Val Phe          #       525                                                                    - Arg Thr Tyr Asn Ala Ser Lys Thr Met Gln As - #p Gln Ile Asp Ile Ile          #   540                                                                        - Glu Asn Glu Gly Thr Val Ala Glu Lys Val Al - #a Lys Phe Asn Ala Ala          545                 5 - #50                 5 - #55                 5 -        #60                                                                            - Asn Arg Thr Val Ala Ile Leu Cys Asn His Gl - #n Arg Thr Val Ser Lys          #               575                                                            - Thr His Gly Asp Ser Val Gln Arg Ile Asn As - #p Lys Leu Lys Lys Phe          #           590                                                                - Met Trp Gln Lys Ile Arg Leu Lys Lys Met Il - #e Leu Gln Leu Glu Pro          #       605                                                                    - Lys Leu Lys Lys Lys Asp Ser Lys Tyr Phe Gl - #u Glu Ile Asp Asp Leu          #   620                                                                        - Leu Lys Glu Asp Ile Glu His Ile His His Th - #r Ile Ile Lys Arg Gln          625                 6 - #30                 6 - #35                 6 -        #40                                                                            - Arg Glu Gln Ala Lys Lys Lys Leu Glu Arg As - #p Asn Glu Lys Leu Lys          #               655                                                            - Leu Glu Gly Lys Pro Leu Leu Thr Glu Ser As - #p Ile Lys Asp Lys Leu          #           670                                                                - Asp Lys Ile Asp Glu Leu Glu Lys Glu Tyr Gl - #n Lys Glu Leu Lys Thr          #       685                                                                    - Gly Lys Pro Ile Val Thr Lys Asn Ala Thr Va - #l Glu Lys Leu Lys Gln          #   700                                                                        - Gln Ile Glu Thr Leu Glu Asn Lys Ile Leu As - #n Val Ser Ile Gln Leu          705                 7 - #10                 7 - #15                 7 -        #20                                                                            - Lys Asp Lys Glu Asp Asn Ser Glu Val Ser Le - #u Gly Thr Ser Lys Met          #               735                                                            - Asn Tyr Ile Asp Pro Arg Leu Ile Val Met Ph - #e Ser Lys Lys Phe Asp          #           750                                                                - Val Pro Ile Glu Lys Leu Phe Thr Lys Thr Le - #u Arg Glu Lys Phe Ile          #       765                                                                    - Trp Ala Ile Glu Ser Ala Asp Glu Asn Trp Ar - #g Phe                          #   780                                                                        __________________________________________________________________________ 

We claim:
 1. A method of identifying inhibitors of C. albicans topoisomerase I protein comprising the steps of:contacting a first host cell which is deficient in a functional topoisomerase gene except for a functional gene that encodes C. albicans topoisomerase I protein with a test compound; contacting a second host cell which is deficient in a functional topoisomerase gene except for a functional gene that encodes non-C. albicans topoisomerase I protein with a test compound; identifying a test compound whose presence results in the death of the first host cell but not the second host cell.
 2. The method of claim 1 wherein said functional gene that encodes C. albicans topoisomerase I protein comprises SEQ ID NO:1.
 3. A method of identifying inhibitors of C. albicans topoisomerase I protein comprising the steps of:contacting a first host cell which is deficient in a functional endogenous topoisomerase I gene with a test compound, wherein said first host organism is an organism other than C. albicans and comprises a functional gene that encodes C. albicans topoisomerase I protein; contacting a second host cell which comprises a functional topoisomerase I gene with a test compound wherein said second host organism is an organism other than C. albicans and is free of a functional gene that encodes C. albicans topoisomerase I protein; identifying a test compound whose presence results in the death of the first host cell but not the second host cell.
 4. The method of claim 3 wherein said functional gene that encodes C. albicans topoisomerase I protein comprises SEQ ID NO:1.
 5. The method of claim 3 wherein said second host cell comprises a functional endogenous topoisomerase I gene.
 6. The method of claim 3 wherein said second host cell is deficient in a functional endogenous topoisomerase I gene and comprises a functional non-endogenous topoisomerase I gene.
 7. The method of claim 3 wherein said second host cell is deficient in a functional endogenous topoisomerase I gene and comprises a functional human heterologous topoisomerase I gene.
 8. The method of claim 3 wherein said first host cell and second host cell are cells of the species selected from the group consisting of Saccharomyces species, Schizosaccharomyces species, Escherichia coli, and Salmonella typhimurium.
 9. The method of claim 3 wherein said first host cell and second host cell are yeast cells.
 10. The method of claim 9 wherein said functional gene that encodes C. albicans topoisomerase I protein comprises SEQ ID NO:1.
 11. The method of claim 9 wherein said second host cell comprises a functional endogenous topoisomerase I gene.
 12. The method of claim 9 wherein said second host cell is deficient in a functional endogenous topoisomerase I gene and comprises a functional non-endogenous topoisomerase I gene.
 13. The method of claim 9 wherein said second host cell is deficient in a functional endogenous topoisomerase I gene and comprises a functional human heterologous topoisomerase I gene. 